1. Field of the Invention
The present invention relates to a non-return valve for supply cocks.
2. Description of Related Art
Valves of the type mentioned are used in conjunction with supply cocks for flexible hosepipes used, for example in the fruit and vegetable sector, in flower growing and the like, or for washing purposes, for example in garages and the like, the said valves constituting valves for preventing contamination of the water supply. The said valves in fact prevent the water supplied from flowing in the opposite direction, i.e from the pipe used for watering, washing or the like, back into the water supply network. As is known, such a return flow would occur if there were a drop in pressure in the water supply upstream of the supply cock (due, for example, to an excessive demand), as a result of which the water inside the pipe, which may be immersed in a full storage tank, would flow, together with the impurities in it, back into the water supply network and contaminate the latter.
The known non-return valves comprise a cover part and a valve-body part. The cover part is in the shape of a cup threaded internally, for joining to a supply cock, and in the bottom of the same there are apertures through which the water to be supplied passes. At the bottom, there is also a seal cooperating with the supply cock. The cover part is also provided with a screw for fixing it to the cock and also has an external thread for screwing it inside the valve body. The latter has the shape of an upturned cup and contains the various operating parts of the valve. The said parts comprise first of all a flexible annular washer supported in a seat at a distance from the bottom of the valve body and designed to cover the said supply apertures and, under the pressure of the water supplied, to uncover the same by resting on an underlying sealing collar. The water supplied thus comes up against the end of a piston-type obturator located underneath and supported movably during opening and against a positioning spring during closure. The constricted base of the valve body is also provided with apertures for discharging the return water, which is discharged externally.
The valves of the known type therefore have a design which requires a large number of components as well as numerous operations for manufacturing the latter. Several washers are also required. Assembly of the individual components involves a large number of operations. The production costs are therefore rather high. The piston-type obturator also reduces considerably the working cross-section of the outlet aperture of these known non-return valves. The said obturator also requires special features to ensure that it is guided perfectly as well as the use of a special closing spring.
Since, for trouble-free operation of these known valves, a movable obturator must be correctly positioned and guided, it is obvious that the presence of impurities in the water, such as grains of sand and the like, could lead to blocking and incorrect positioning of the said obturator.